The Obesity Epidemic Is Accelerating Worldwide

A new study with data from 18 countries shows frightening developments.

Posted Feb 18, 2020

Obesity is one of the leading causes of preventable death worldwide. According to the World Health Organization (WHO), worldwide obesity has nearly tripled since 1975. In 2016, about 13% of the world’s adult population (11% of men and 15% of women) were obese.

How is Obesity Defined?

The National Institute of Health uses the so-called BMI (body mass index) to this end. BMI is a value that roughly indicates whether someone is underweight, overweight, obese or has normal weight. It is derived by taking the body mass in kilograms and dividing it by the square of the body height. For example, someone with a body mass of 80 kilograms (about 176 pounds) and a body height of 1.8 meters (about 5 feet and 10.8 inches) would have a BMI of 80/1.82 = 24.7 kg/m2.

According to the National Heart, Lung and Blood Institute, the following weight categories can be derived from the BMI:

  • Underweight: BMI <18.5
  • Normal weight: BMI 18.5–24.9 
  • Overweight: BMI 25–29.9 
  • Obesity: BMI >30
  • Extreme Obesity: BMI >40 

The BMI itself and the cut-off values for different categories have criticized for a number of reasons. For example, it has been argued that very muscular individuals are often categorized as overweight, even though they have a relatively low amount of body fat. Also, tall people often have a BMI that is too high, while shorter people have one that is too low since height has a large impact on BMI as it is being squared. This indicates that on the individual level, it makes a lot of sense to make a personal assessment that factors in more variables than BMI when determining whether someone has a healthy weight or not.

However, on the population level, looking at average BMI’s over time gives a good estimate of whether people on average get more obese or not. A new scientific paper that has just been published in Obesity Reviews, an official journal of the International Association for the Study of Obesity now did that and revealed frightening results (Williamson et al., 2020). The authors looked specifically at extreme obesity, that is whether someone has a BMI over 40. 

Just to give an example: The average male height is 5.6 ft. In order to have a BMI of over 40, a person with that height would need a weight of more than 248 pounds. Compared to someone with normal weight, individuals suffering from extreme obesity have an extremely higher risk of developing type 2 diabetes, hypertension, and cardiovascular disease (NHLBI). These are serious conditions that can lead to premature death.

In their study, Williamson et al., (2020) included data about people with a BMI over 40 from national surveys from 18 individual countries, on all five continents. They found that for men and women combined, the USA had the highest percentage of adults with a BMI over 40 (7.7%), while Spain had the lowest percentage (1.3%) of all investigated countries. When only men were investigated, the percentages ranged between 0.7% in Serbia and 5.6% in the USA. When only women were investigated, the percentages ranged between 1.8% in Poland and 9.7% in the USA. Importantly, there was a statistically significant growth of people with a BMI over 40 over that last decades, indicating that extreme obesity is increasing worldwide.

The authors highlight that more research into people with extreme obesity is needed, as their medical and psychological needs might need special attention compared to other people. For example, the appropriate dosage of medicines might differ from other people and extremely obese people might face social stigma which could lead to many psychological issues.


Williamson K, Nimegeer A, Lean M. (2020). Rising prevalence of BMI ≥40 kg/m2 : A high-demand epidemic needing better documentation. Obes Rev, in press.